Anole Annals

Aerial Behavior by Anolis pentaprion

On March 18, 2014

Anolis pentaprion taxiing down the runway on a canopy tower at the La Selva Biological Station in Costa Rica. Photo by Vinicio Paniagua.

Draco, the flying dragon, has borrowed an anole dewlap, so it’s only proper that anoles return the favor by developing gliding capabilities. It’s been long rumored that Anolis pentaprion, a twig anole from Central America, will launch itself off of perches in canopy and glide away, but now Steve Overbauer, Vinicio Paniagua, Craig Guyer and Mo Donnelly have documented just that in an interesting herpetological natural history note that appeared in the last issue of last year’s volume of Herp Review (Vol. 44, pp. 677-678). Here’s what they have to say:

“Lizards with gliding or directed aerial descent behaviors are well known from the Old World Tropics (e.g., Draco, Ptychozoon), and snakes and frogs exhibiting these behaviors are found both in the Old and New World Tropics (Dudley et al. 2007. Annu. Rev. Ecol. Evol. Syst. 38:179–201). However, lizards showing directed aerial descent have not been reported from the New World Tropics. Here we report on directed aerial descent capability and behavior in Norops pentaprion, a canopy lizard from eastern Costa Rica, southern Nicaragua, and western Panama (Köhler 2010. Zootaxa 2354:1–18).

The initial discovery of this behavior in N. pentaprion was serendipitous in July 2001 when an individual was captured on a walk-up meteorological tower at canopy level (~ 25 m) at La Selva Biological Station in the Atlantic lowlands of Costa Rica. After identification, the animal was returned to the original location on the tower, but upon release to a horizontal tower brace, it executed a controlled aerial descent to a tree in the distance below. Individuals of N. pentaprion have been occasionally observed on our meteorological towers subsequent to our first observation of directed aerial descent. The lizards are typically at canopy level but are sometimes found well above the canopy on the highest levels of the towers (up to 42 m). While the typical response of N. pentaprion to the presence of personnel on the tower is to race down the tower or hide on the opposite side of vertical supports, the animals will occasionally jump from the tower to escape when approached. Since 2001 we have observed directed aerial descent by N. pentaprion from canopy towers on several occasions. In at least two instances the lizard landed at lower levels on the tower, but in other occurrences they covered substantial distance to adjacent trees including aerial rotations of near 180º. During more than one observation, animals appeared to glide with near-horizontal trajectories towards termination of the descent. Similar to some snakes, frogs, lizards, and ants showing directed aerial descent, N. pentaprion does not have strongly specialized features associated with gliding behavior such as skin flaps, skin extensions, or webbed feet. Norops pentaprion has a relatively flattened head and wide body. During aerial descent this lizard proceeds headfirst, with limbs partially extended and the body strongly flattened, a position that may take advantage of regions of relatively loose skin along the sides of the body (Guyer and Donnelly 2005. Amphibians and Reptiles of La Selva, Costa Rica, and the Caribbean Slope, Univ. California Press, Berkeley, California. 299 pp.).

At La Selva Biological Station this species is uncommon in the understory and is usually found on trees limbs. Norops pentaprion is a member of a closely-related group of anoline lizards subjected to a recent analysis of morphology and morphometrics (Köhler, op. cit.); these related taxa share similar body size characteristics with N. pentaprion and are frequently arboreal. Future observations of some of these species may result in the discovery of similar directed-aerial descent behavior. Canopy pioneer Donald Perry reported lizards with a rose dewlap parachuting between trees in the canopy in Costa Rican forests (Perry 1986. Life Above the Jungle Floor, Simon and Schuster, Inc. New York, New York. 170 pp.), but the species was not identified. In their description of Norops pentaprion, Guyer and Donnelly (op. cit.) indicated that parachuting behavior likely occurs in this species on the basis of our initial observations and those of Perry. Our repeated observations verify directed aerial descent in this species and confirm that the lizard observed by Perry was N. pentaprion, the only lizard in the region with magenta dewlap coloration.”

More Studies on Anole Chromosomes

By Jonathan Losos

On March 16, 2014

In New Research

When it rains, it pours. Research on the immense diversity in anole chromosomes was rampant in the 1970’s and early 1980’s, and then…nothing. Until, that is, the last two months. Not one, but two, papers appeared in Evolution, and now AA has learned of a paper on chromosomal variation in Norops clade anoles, recently published in Zoological Studies (click for a downloadable pdf). The paper, by Castiglia et al., examines karyotypes in Norops anoles and argues that karyological variation is in some cases consistent with our understanding of phylogenetic relationships within the group.

Abstract
Background: Neotropical lizards, genus Anolis (Polychrotidae), with nearly 380 species, are members of one of the most diversified genera among amniotes. Herein, we present an overview of chromosomal evolution in ‘beta’ Anolis (Norops group) as a baseline for future studies of the karyotypic evolution of anoles. We evaluated all available information concerning karyotypes of Norops, including original data on a recently described species, Anolis unilobatus. We used the phylogeny of Norops based on DNA sequence data to infer the main pattern of chromosomal evolution by means of an ancestral state analysis (ASR).

Results: We identified 11 different karyotypes, of which 9 in the species had so far been used in molecular studies. The ASR indicated that a change in the number of microchromosomes was the first evolutionary step, followed by an increase in chromosome numbers, likely due to centric fissions of macrochromosomes. The ASR also showed that in nine species, heteromorphic sex chromosomes most probably originated from six independent events.

Conclusions: We observed an overall good correspondence of some characteristics of karyotypes and species relationships. Moreover, the clade seems prone to sex chromosome diversification, and the origins of five of these heteromorphic sex chromosome variants seem to be recent as they appear at the tip nodes in the ancestral character reconstruction. Karyotypic diversification in Norops provides an opportunity to test the chromosomal speciation models and is expected to be useful in studying relationships among anole species and in identifying cryptic taxa.

Available Now: A New, Large Phylogeny of Anoles

By Anthony J Geneva

On March 14, 2014

In New Research, Research Methods

BEAST estimated phylogeny of anoles. Circles on nodes represent posterior probability, black > 0.95, grey > 0.90, white > 0.70.

In the course of our recent study on sex chromosome evolution in anoles (Gamble et al. in press) [AA post] we assembled a 216-species mitochondrial DNA phylogeny of anoles, the largest published to date (at least that we know of), yet containing only a little more than half of all recognized species. Although we collected new sequences for some species, our dataset is largely built on the hard work of others who collected and published on sequences from across the genus, such as Jackman et al. 1999, Poe 2004, Nicholson et al. 2005, Mahler et al. 2010 [AA post], and Castañeda & de Quieroz 2011 [AA post]. Without access to data from these and other studies, we would have had a far less complete and robust tree for our comparative analyses.

There is a big debate going on now regarding what, where and how much data should be shared in association with publishing academically. I personally feel that providing easy access to those data used and generated during a study serves to accelerate the rate and increase the quality of scientific discovery. I am heartened that more and more journals are making data deposition a requirement for publication, although often this means little more than dumping sequence data to GenBank. Sites like Dryad, Figshare, and GitHub now provide open, permanent, and citable access to raw data, figures and, most importantly in my view, research products like alignments, code and analysis logs. In an effort to make our data as accessible and useful as possible we have archived our alignment, MrBayes and BEAST consensus trees as well as as the BEAST posterior distribution on the digital data repository Dryad [doi link]. It is our hope that other anolologists can use and improve upon these data to ask new, interesting questions and to build a larger, more complete view of the evolution of anoles.

Anolis stratulus Displaying

By Jonathan Losos

On March 13, 2014

In All Posts

Note the arm waving and tongue protrusion!

httpv://www.youtube.com/watch?v=OP3rnPQJT6A

How to Set Up a Lizard Room to House and Breed Anoles

By Jonathan Losos

On March 11, 2014

In All Posts

Thinking of setting up a room to maintain and breed lizards for research projects? Back in 2011, the good folks in the Glor Lab–which has done a stupendous job at breeding A. distichus–shared their accumulated knowledge in an 11-part series. Given the fog of memory, it seemed like a good time to remind the world of the existence of this primer, and put the links all together in one place.

So, with no further ado, here are the 11 posts in the “Evolution of a Lizard Room” undecology:

1: Introduction

2: Maintaining humidity

3: The watering wand

4: Crickets

5: The Shopvac

6: Generating food in house

7: Egg-laying

8: Egg inculation

9: Toe clipping

10: Custom cages for breeding experiments

11: Butterfly Cages

For another source of information, check-out the manual put together by the Brodie Lab at the University of Virginia.

Anolis allisoni Featured in Film on Reptile Diversity of Cayos Cochinos, Honduras

By Jonathan Losos

On March 10, 2014

In All Posts

httpv://www.youtube.com/watch?v=WyGO_rcVEM0

We’ve had previous posts [1,2] on research on anoles of these islands. Nice footage of ctenosaurs and boas as well.

50% Off Anole Watches for Next 2.5 Hours

By Jonathan Losos

On March 9, 2014

In All Posts

What better way to celebrate moving your clock forward than getting that anole watch–available in five ecomorphs–that you’ve been coveting. Pop on over to Zazzle.com now, and don’t delay, because the deal ends at 1 p.m. Eastern Daylight Time. Use code word sundaydeal22.

What Makes Anolis Communities Complete?

By Katharina Wollenberg Valero

On March 7, 2014

In All Posts

One of my favorite graphic representations of a typical anole community is the one where all ecomorphs are hanging out together in a tree and a scrub next to said tree. Each ecomorph has its structural microhabitat place and they are all spaced out evenly across the tree to represent competition. Originally the figure was published by Williams (1983) and then modified later on. Arriving on the Greater Antilles, one thus expects to promptly be able to say hi to all these ecomorphs at the next best tree. Well, from my personal experience, I can tell you that this is unfortunately not the case.

Localities where all ecomorphs are found together are scarce, and all of them are famous, having served as field sites for the most groundbreaking of anole discoveries. But what about the rest of them? Something must prevent the co-occurrence of ecomorphs in all these other places. This was noted before: Losos (2009) remarked that all utilized structural microhabitats exploited by all ecomorphs are present throughout the islands, so “complete” ecomorph communities should also be able to occur everywhere.

A common explanation for the absence of certain “functional types” (= Anolis ecomorphs) from local communities is a process that is called “filtering.” Modern community assembly theory distinguishes two such types of filters: 1. Biotic interaction filters and 2. Environmental filters.

Biotic filtering involves competitive exclusion: For anoles this phenomenon caused ecological speciation which led to the convergent evolution of the ecomorph communities. But biotic filtering should not be expected to occur at this stage of the radiation: Different ecomorphs are not competing for the same structural microhabitat niche in different localities. This leaves environmental filtering. In our study recently published in Ecology and Evolution, on which I am reporting here, we tested whether environmental filtering could be a possible explanation for the absence of ecomorphs in local communities.

First, we modeled Anolis ecomorph community completeness by constructing environmental niche models for each ecomorph (the sum of species belonging to that ecomorph) on each island. These models were then overlaid for all ecomorphs per island.

The map for ecomorph community completeness shows a very patchy distribution of areas where all ecomorphs are expected to occur. Comparisons of environmental niches among these islands revealed that only Hispaniola and Cuba have their complete Anolis ecomorph communities occurring in a similar bioclimatic parameter space.

This patchiness could be explained by elevation for all islands except Jamaica: the Anolis community completeness map strongly resembles the topographic relief of the Greater Antilles. Looking more closely into the climatic parameters, Jamaica has much lower daily and annual temperature ranges which are also not related to the island’s elevation, whereas in the rest of the Greater Antillean islands, they are. Occurrence probability of ecomorphs seems to be coupled to environmental parameters, which explains why some ecomorphs are “filtered out“ in some locations: they do not encounter a favorable environment there.

Since I mentioned initially that filtering relates to “functional types” (not species), the filtering must be a result of certain functional properties of the Anolis ecomorphs’ phenotype. We wanted to take the study a step further and actually investigate one (among many) possible functional trait: body mass.

Advice Needed: Field Sites for A. sagrei in Florida

By Katie Boronow

On March 6, 2014

In All Posts

Anolis sagrei. Photo by Janson Jones.

I’m planning an in-depth behavioral study of Anolis sagrei for the summer and need your help finding suitable field sites in Florida.

My ideal location would have the following traits:

– Abundant A. sagrei in an area large enough to support at least 50 adult males

– Relatively open understory

– Not heavily trafficked by people (I’d like to minimize the frequency of behavioral trials being disrupted by inquisitive passersby), but still safe to work in

– Management receptive to researchers

Does anyone know of protected areas, biological or agricultural field stations, or other underutilized green spaces that might fit the bill? I’m open to locations throughout the state.

Thanks in advance for any suggestions!

Exploring the Anolis Y Chromosome

By Tony Gamble

On March 5, 2014

In Anole Genome Research, New Research

Sex chromosomes have historically been identified by inspecting chromosome spreads under a light microscope and looking for a morphologically distinct or heteromorphic pair of chromosomes – typically and X and Y or a Z and W. However, heteromorphic sex chromosomes are absent in many animal groups, particularly fish, amphibians, and lizards, making it difficult to determine whether a species with genetic sex determination has an XY or ZW system. As a consequence, the study by staustinreview.com of sex chromosome evolution in clades in which cryptic or homomorphic sex chromosomes are prevalent has been hampered by a lack of identified sex chromosomes in these groups. New methods are needed to find the sex chromosomes in these species and increase our understanding of homomorphic sex chromosome biology, the evolution of sex determining systems, and patterns of sex chromosome evolution overall.

David Zarkower and I have a paper in press at Molecular Ecology Resources that uses high-throughput DNA sequencing to identify sex-specific genetic markers as a means to reveal sex chromosome systems in species that lack heteromorphic sex chromosomes. We are using a newly developed DNA sequencing technique called restriction site associated DNA sequencing or RAD-seq. RAD-seq sequences the DNA flanking very specific DNA sequences (restriction enzyme recognition sites) scattered throughout the genome, generating tens of thousands of genetic markers. RAD-seq is a powerful technique for exploring genetic variation in ‘nonmodel’ species because it does not require a fully sequenced genome, requires relatively modest sequencing capacity, and can detect even minor genetic differences among individuals. We are using RAD-seq to 1) identify sex-specific molecular markers (i.e., bits of DNA found in individuals from one sex but not the other), and 2) using these markers to determine whether a species has XY or ZW sex chromosomes. Species with male-specific markers will have an XY system while species with female-specific will have a ZW system.

We are interested in using RAD-seq to screen various vertebrate species for sex chromosomes, but first wanted to validate the technique using a species with a known sex-determining mechanism. We chose the green anole (Anolis carolinensis) because its X and Y chromosomes are small and homomorphic. Therefore A. carolinensis sex chromosomes should provide a rigorous test of this technique and success with Anolis suggests there may be broad utility using this technique in other groups with homomorphic sex chromosomes.

We performed RAD-seq on seven male and ten female A. carolinensis and recovered one male-specific molecular marker. We confirmed that the marker was male-specific using PCR and also found that this genetic marker is conserved in some additional Anolis species, confirming homology among the Y chromosomes of these species (Anolis sex chromosome homology has been discussed previously on Anole Annals 1, 2). These results highlight the potential utility of RAD-seq as a tool to discover the sex chromosome systems of large numbers of species in a rapid, cost-effective manner.

PCR validation of the male-specific RAD-seq marker in Anolis carolinensis.

In addition to learning about Anolis sex chromosomes the male-specific molecular marker we identified can be used to sex individuals of many Anolis species using a simple PCR-based assay, particularly species in the A. carolinensis group and in the Norops clade. This enables identification of an individual’s sex prior to the onset of secondary sexual characteristics, for example in embryos, thereby aiding developmental studies of sexually dimorphic phenotypes. The importance of sexual dimorphism to Anolis ecology and evolution has been examined previously (1, 2, 3, 4), but there is certainly much more to learn, particularly about how sexually dimorphic traits develop and evolve. The ability to sex Anolis embryos is an important step to advance this research.

Phylogenetic relationships among sampled species illustrating the sex-specific amplification of the gene rtdr1y in selected anole species. The autosomal gene kank1 was used as an internal positive control in all reactions. Bands labelled with ‘NS’ are nonspecific PCR products.

Phylogenetic relationships among sampled anoles illustrating the sex-specific amplification of the gene rtdr1y in selected anole species. The autosomal gene kank1 was used as an internal positive control in all PCR reactions. Bands labelled with ‘NS’ are nonspecific PCR products.